Collection devices are a type of cap and vessel combination commonly used for receiving and storing biological specimens for delivery to clinical laboratories, where the specimens may be analyzed to determine the existence or state of a particular condition or the presence of a particular infectious agent, such as a virus or bacterial microorganism. Types of biological specimens commonly collected and delivered to clinical laboratories for analysis include blood, urine, sputum, saliva, pus, mucous and cerebrospinal fluid. Since these specimen-types may contain pathogenic organisms, it is important to ensure that collection devices are constructed to be substantially leak-proof during transport from the site of collection to the site of analysis. This feature of collection devices is especially important when the clinical laboratory and the collection facility are remote from one another, increasing the likelihood that the collection device will be inverted or severely jostled during transport and potentially subjected to substantial temperature and pressure fluctuations.
To prevent specimen leakage, and possible contamination of the surrounding environment, collection device caps are typically designed to be screwed, snapped or otherwise frictionally fitted or welded onto the vessel component, thereby forming a substantially leak-proof seal between the cap and the vessel. In addition to preventing fluid specimen from leaking, a substantially leak-proof seal formed between the cap and the vessel components of a collection device may also aid in ameliorating exposure of the specimen to potentially contaminating influences from the immediate environment. This aspect of a leak-proof seal is important for preventing the introduction of contaminants into the collection device that could alter the qualitative or quantitative results of an assay.
While a leak-proof seal should prevent specimen seepage during transport, the actual removal of the cap from the vessel prior to specimen analysis presents another potential opportunity for contamination. When removing the cap, specimen which may have collected on the underside of the cap during transport could come into contact with a clinician, possibly exposing the clinician to a harmful pathogen present in the fluid sample. And if the specimen is proteinaceous or mucoid in nature, or if the transport medium contains detergents or surfactants, then a film or bubbles could form around the mouth of the vessel during transport which could burst when the cap is removed from the vessel, thereby disseminating specimen into the testing environment. Another risk associated with cap removal is the potential for creating a contaminating aerosol which may lead to false positives or exaggerated results in other specimens being simultaneously or subsequently assayed in the same general work area through cross-contamination. It is also possible that specimen residue from one collection device, which may have been inadvertently transferred to a gloved hand of a clinician, will come into contact with specimen from another collection device through routine or careless removal of caps and handling of the collection devices.
Concerns with cross-contamination are especially acute when the assay being performed involves nucleic acid detection and includes an amplification procedure such as the well known polymerase chain reaction (PCR), or a transcription-based amplification system such as transcription-mediated amplification (TMA). (A review of several amplification procedures currently in use, including PCR and TMA, is provided in HELEN H. LEE ET AL., NUCLEIC ACID AMPLIFICATION TECHNOLOGIES (1997).) Since amplification is intended to enhance assay sensitivity by increasing the quantity of targeted nucleic acid sequences present in a specimen, transferring even a minute amount of pathogen-bearing specimen from one vessel, or target nucleic acid from a positive control sample, to another vessel containing an otherwise negative specimen could result in a false-positive result.
To minimize the potential for creating contaminating specimen aerosols, and to limit direct contact between specimens and humans or the environment, it is desirable to have a collection device cap which can be penetrated by a fluid transfer device (e.g., a pipette tip which can be used with an air displacement pipette) while the cap remains physically and sealably associated with the vessel. The material and construction of the penetrable aspect of the cap should facilitate the venting of air displaced from the interior space of the collection device to ensure accurate fluid transfers and to prevent a rapid release of aerosols as the fluid transfer device is being inserted into or withdrawn from the collection device. And, because air is vented from the interior space of the collection device after the cap has been penetrated, it would be particularly helpful if means were included for minimizing aerosol release through the cap once it was penetrated by the fluid transfer device. Also, to limit the amount of potentially contaminating fluid present on the exterior of the fluid transfer device after it is has been withdrawn from the collection device, it would be advantageous if the cap also included means for wiping or absorbing fluid present on the outside of the fluid transfer device as it is being withdrawn from the collection device. To prevent damage to the fluid transfer device which could affect its ability to predictably and reliably dispense or draw fluids, and to facilitate its use in manual pipetting applications, the cap should also be designed to limit the forces necessary for the fluid transfer device to penetrate the cap. Ideally, the collection device could be used in both manual and automated formats and would be suitable for use with disposable pipette tips made of a plastic material.
Collection device caps which can be penetrated by a fluid transfer device will have other advantages, as well, including the time-savings resulting from clinicians not having to manually remove caps from vessels before retrieving sample aliquots from the collection devices for assaying. Another advantage of penetrable collection device caps would be the reduction in repetitive motion injuries suffered by clinicians from repeatedly unscrewing caps.